WateringTimesWatering plan, $19
Fatsia japonica (SHADE), WUCOLS IV

How often to water Japanese aralia in California

In July in the Central Valley, established Japanese aralia in loam needs a deep watering about every 20 days: about 8.8 gallons each time for a plant 4 feet across, about 3.0 gallons a week. Japanese aralia, or fatsia, is an evergreen shrub with a tropical look, grown for glossy, deeply lobed leaves that can reach 18 inches across. Round clusters of white flowers open in autumn, followed by black berries in winter. It needs shade, since leaves brown in full sun or wind, and it grows best in moist, well-drained, rich soil.

ShrubRated for 5 of 6 zones

How often to water Japanese aralia, month by month

Your city
Plant width
4 ft
Your soil

Type your city above and the days between waterings and the gallons appear here, worked out from your city's climate table. Or read the figures by climate zone further down.

Every month, on your water days. The personal plan prints this for Japanese aralia and the rest of your yard, on the days your water supplier allows.Get the plan for $19

How this is worked out: established roots fill the top 1.5 feet of soil, and you water again when that soil has dried halfway. Loam soil holds about 1.5 inches of water per foot. Water the whole area the plant covers, and skip a watering after a good soaking rain.

Which soil do you have?

Dig down a few inches, take a handful of moist soil and squeeze it.

  • Sandy: gritty, falls apart when you open your hand, will not form a ball.
  • Loam: forms a soft ball that crumbles when you poke it.
  • Clay: forms a firm, sticky ball and squeezes out into a ribbon between thumb and finger.

Still not sure? Pick loam. Most garden beds sit between sand and clay.

How to measure plant width

A shrub with its width marked from one side to the other and the circle under it shaded blue

Measure across the plant, from the tips of the leaves on one side to the tips on the other.

Water the whole area the plant covers, shown in blue. The gallons here cover that area.

A wider plant means more gallons each watering, not more waterings. While it is young, measure again each spring.

How to tell it needs water

  • Soil dry 2 to 3 inches down beneath the big leaves means Japanese aralia needs water
  • Large leaves drooping by afternoon and still limp the next morning point to a dry root zone
  • Brown, scorched patches on the leaves usually mean too much sun or wind, not too little water
  • Yellowing lower leaves and a soft stem base in soggy soil point to root rot from excess moisture
  • Sticky leaves or fine webbing on plants kept indoors point to aphids, scale or spider mites

How to water it

  • Water Japanese aralia at the base under the leaf canopy with drip or a soaker
  • Soak the root zone about a foot deep, then let the top couple of inches dry before watering again
  • Plant in part to full shade, out of wind, in rich, moist soil that drains
  • Mulch with leaf mold or compost to keep the soil cool and evenly moist
  • Widen the watered area as the shrub fills out toward 4 to 6 feet across

Through the seasons

Keep a new Japanese aralia's root ball moist through the first summer, then shift to deeper soakings with some drying between. Once established it tolerates short dry spells but looks best with steady moisture. The plant is evergreen, blooms in autumn and carries black berries in winter, so it draws some water all year. In the low desert, shade is essential. Its WUCOLS rating is moderate water on the north-central coast, the south coast, South Inland and the low desert. Its Central Valley rating is low water. WUCOLS marks it as not suited to the high desert.

In pots

Japanese aralia is a classic container plant for shaded patios and bright indoor rooms. Use a pot with drainage holes and a rich, well-drained mix. Outdoors in summer heat, check 2 inches down every few days and water when dry. Indoors, lower light slows drying, so check before watering. Empty the saucer each time. In winter, water less and keep the pot out of cold, drying wind.

1 Your climate zone six WUCOLS zones, each from its own reference city
1.07gal per sq ft in JulyLow water use in the Central Valley zone
A year
6.84 gal per sq ft
Reference
Sacramento climate table
Counts
Plant need, before sprinkler losses
0.711.42.12.90.16JAN0.26FEB0.43MAR0.61APR0.83MAY0.99JUN1.07JUL0.95AUG0.72SEP0.47OCT0.22NOV0.14DEC0.711.42.12.90.16JFM0.61AMJ1.07JAS0.47OND
Gallons per square foot per month, Central Valley. Peak 1.07 in Jul, 6.84 a year.

Monthly water need by climate zone

Japanese Aralia: gallons per square foot per month, by WUCOLS climate zone

MonthN. CoastC. ValleyS. CoastS. InlandHi DesertLo Desert
Jan0.370.160.780.78–0.78
Feb0.530.260.810.87–0.93
Mar0.870.431.151.3–1.52
Apr1.180.611.41.61–1.95
May1.460.831.611.95–2.45
Jun1.610.991.742.29–2.79
Jul1.611.071.982.51–2.85
Aug1.490.951.862.33–2.6
Sep1.240.721.491.86–2.08
Oct0.870.471.151.33–1.49
Nov0.470.220.840.9–0.96
Dec0.310.140.650.68–0.68
Year126.8415.518.41–21.08

How this is worked out: the WUCOLS water rating for each zone times that zone’s climate for the month. A dash means WUCOLS does not rate the plant there. The figures are what the plant uses, before sprinkler losses.

Plants with the same water needs 16

Rated low water in the Central Valley, like Japanese aralia. Plants that drink alike can share one valve and one schedule.

LavenderLavandula spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyRosemaryRosmarinus officinalislow water, Central Valley1.07 gal/sq ft in JulyBougainvilleaBougainvillea & spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyOlive TreesOlea europaea ssp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyCrape MyrtleLagerstroemia spp., hybrids & cvs.low water, Central Valley1.07 gal/sq ft in JulyLantanaLantana camara ssp. & cvs.low water, Central Valley1.07 gal/sq ft in JulySalviaSalvia greggii ssp., cvs. & hybridslow water, Central Valley1.07 gal/sq ft in JulyAloeAloe spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulySucculentsEcheveria spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyJunipersJuniperus spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulyRussian SagePerovskia spp. & cvs.low water, Central Valley1.07 gal/sq ft in JulySagebrushArtemisia spp. (shrubby)low water, Central Valley1.07 gal/sq ft in JulyWild PrivetLigustrum vulgarelow water, Central Valley1.07 gal/sq ft in JulyCoralberrySymphoricarpos orbiculatus (SHADE)low water, Central Valley1.07 gal/sq ft in JulySydney Golden WattleAcacia longifolialow water, Central Valley1.07 gal/sq ft in JulyBlue Leaf WattleAcacia salignalow water, Central Valley1.07 gal/sq ft in July
Minutes for your sprinklers

Turn this into minutes on your water days

Every city page has a calculator that takes Japanese aralia, your sprinkler type and the month, and gives the minutes per water day for that supplier's schedule. Or put it in a zone of the personal watering plan and get all twelve months printed.

Questions people ask

How often should I water Japanese aralia in summer?

In July, established Japanese aralia in loam needs a deep watering about every 20 days in the Central Valley, about every 11 days on the south coast and about every 9 days in the South Inland zone. Sandy soil holds less water, so waterings come closer together. Clay stretches them. Check the soil before each watering and skip one after a soaking rain.

How much water does Japanese aralia need per day?

In July in the Central Valley, established Japanese aralia needs about 0.4 gallons a day for a plant 4 feet across and about 1.7 gallons a day for a plant 8 feet across. Give it in deep waterings spread days apart rather than a little every day, so the whole root zone gets wet.

Does watering for Japanese aralia change across California?

Yes. WUCOLS rates Japanese aralia separately for each of the six California climate zones: moderate water in the North-Central Coastal zone, low water in the Central Valley zone, moderate water in the South Coastal zone, moderate water in the South Inland zone, not suited to this region in the High and Intermediate Desert zone, moderate water in the Low Desert zone. The monthly table above shows how the same rating translates into different gallon amounts as reference evapotranspiration changes.

Why are my fatsia leaves turning brown?

Too much sun or wind is the usual cause, since the large leaves scorch easily. Move a pot into shade or shelter a planted shrub. Check the soil too, because a dry root ball adds to the damage.

Can Japanese aralia grow indoors?

Yes, it is a common houseplant. Indoors it dries more slowly, so water when the top inch or two of mix is dry. Watch for aphids, scale, mealybugs and spider mites on indoor plants.

Does Japanese aralia flower?

Yes. It blooms in autumn with ball-shaped white flower heads, and small black berries ripen in mid to late winter. The plant keeps drawing water while it flowers and fruits.

Can Japanese aralia take salt spray?

It tolerates salt spray and pollution, so it can work in coastal and city gardens. Keep it in shade and out of strong wind even there.

Can you overwater Japanese aralia?

Yes. Excess moisture can cause root rot. Let the top couple of inches dry between waterings, especially in winter and indoors.

More plant watering guides

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Sources